Process of manufacturing polymerization products



30 arts.

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UNITED STATES PROCESS OF MANUFACTURING POLYMER- IZATION PRODUCTS Daniel E. Strain, Wilmington, Del;, asslgnor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application April 26, 1933, Serial No. 668,080. Renewed October 1, 1937 7 Claims.

This invention relates to the production of synthetic resins and particularly to an improved process for the manufacture of products of polymerization or inter-polymerization of methyl 5, methacrylate (methyl ester of alpha-methylacrylic acid).

The previously unknown methyl methacrylate and the polymerization products thereof are described in Rowland Hill Patent No. 1,980,483, of November 13, 1934.

In the application of these polymerization products to the industrial arts it has been found that the direct polymerization of the monomeric raw material yields a product which it is difficult to reduce to the finely divided form desirable and sometimes necessary, as, for instance, for the manufacture of molding compositions, lacquers,

'enamels, etc. That is to say, if methyl methacrylate is subjected to polymerizing conditions, e. g. to the action of heat, light, and/or a polymerizing catalyst, the product obtained is generally in a more or less massive form which, because of the inherent properties of the material, it. is diflicult to convert into powders or solutions. It is the object of the present invention to provide an improved process for the manufacture of synthetic resins of the type referred to whereby the products are obtained in a physical form di rectly adapted to the use thereof in the applied Other obiects and advantages of the invention will beapparent as it is better understood by reference to the following specification in which its details and preferred embodiments are described. 35 In accordance with the invention the liquid monomeric methyl ester of methacrylic acid is subjected to polymerizing conditions in the presence of a solvent medium in which the monomer is freely soluble but the polymerized product insoluble or only slightly soluble under the conditions of polymerization. The solvent medium may be added during the course of polymerization, but preferably the monomer is dissolved initially in the solvent and the solution subjected to polymerizing conditions. As polymerization proceeds and the solubility limits of the polymer in the solvent'medium are exceeded, the polymer precipitates in a form varying somewhat with the 'speciflc conditions, but generally as a mushy or gel-like mass, which may readily be broken up by shaking or stirring. The polymer is separated from the solvent and unconverted monomer by filtration, centrifuginmor the like, and, after 55 washing, it dried at a suitably elevated. temperature to remove excess solvent and traces of monomer.

A variety of solvents and solvent combinations are available for the purpose, the particular solvent medium to be chosen depending, inter alia, upon the specific conditions, e; g., the temperature,under which it is desired to effect polymerization. Since polymerized methyl methacrylate is characterized by solubility in an unusual number of liquids, the simple solvents available for the 0 purpose are somewhat limited in number. The aliphatic alchohols, aliphatic ethers, gasoline, and similar aliphatic hydrocarbon and alicylic hydrocarbons are the most suitable of this class. It has been found that the most satisfactory 501- vent medium comprises water, in which both monomer and polymer are insoluble, and a watersoluble solvent for the monomeric material, such as water-soluble monohydric aliphatic alcohols, for example methyl, ethyl, and propyl alcohols, low boiling derivatives of the polyhydric alcohols, such as aikyl ethers of ethylene and diethylene glycol, water-soluble ketones, such as dimethyl and methyl-ethyl ketone, and watersoluble organic acids, such as formic, acetic, and propionic acids.

It is advantageous to employ a solvent medium of such boiling point that it can be removed from the polymer by evaporation at a temperature not exceeding that at which the resin will flow.

Although the process is, under any circumstances, a marked improvement over methods previously employed for the purpose, it has been found that the best results are obtained when the proportion of monomer to totalvolume of monomer and solvent medium is not in excess of 22% by volume. Operating within these limits, the polymeric product can generally be broken up merely by shaking, whereas with a larger proportion of monomer, although the cost of solvent and separation thereof is less, and the timerequired for polymerization somewhat shorter, the particles of polymer adhere to each other and to the sides of the reaction vessel. It is preferred, therefore, to operate within the limits stated. It has also been found that the character of the product is greatly improved by subjecting the solution of monomer to agitation during polymerization, e. g. by shaking or preferably by stirring. This to a large extent inhibits coalescing of the particles of polymer, greatly facilitates removal from the polymerizing vessel, and makes the product more readily comminuted.

It is to be understood that, while the invention is particularly applicable to polymerization of methyl methacrylate by simple application of heat, other-polymerizing agents, either alternatively or additionally, as, for instance, ht (especially ultra-violet light) and/or catalysts, such, for example, as benzoyl peroxide may be used. v

While in the following examples the invention is described with reference to certain specific proportions of materials and operating conditions, it is to be understood that the examples are merely illustrative and that the invention is not limited, thereto.

Example 1.-A solutionoi 20 parts by weight of methyl methacrylate, 40 parts methyl alcohol, and 40 parts water was maintained at 65 C. in a closed vessel for four days. cipitated from solution as formed, yielding a finely divided spongy mass. The methanol-water solution was filtered oil and the product washed with methanol, dried at room temperature for a few hours, and then dried at .140 C. for eight hours. The powdery polymer was in a form adapted directly for use in molding compositions and for the preparation of lacquers.

Example 2.-A solution of 20 parts by weight methyl methacrylate, 40 parts methanol, and 40 parts water was exposed six days at room temperature to the light from a mercury vapor arc.

The polymer formed as a. loose mass which was for the most part converted to a slurry by shaking the polymerization vessel. The product was filtered and dried.

Example 3.A solution of parts (by volume) methyl methacrylate, 40 parts methanol, and 50 parts water was exposed to the light from a mer-.

cury vapor are for eight days. The polymerized methyl methacrylate separated out as a spongy porous material which could be worked into a slurry by shaking or stirring. The polymer was separated from the liquids present and dried at 100 C.

Example 4.--A solution of parts (by weight) methyl methacrylate, parts methanol, 40 parts water, and 0.02 part benzoyl peroxide was maintained at 50 C. for five days. The polymer precipitated from solution as formed, yielding a finely divided spongy mass which could be broken up easily by stirring. from the methanol-water solution, washed with methanol, air dried three hoin-s, and dried at 120 C. for twelve hours. The dried material is light and fiufiy, and can be easily reduced to a powder.

Example 5.A' solution of 7.8 parts (by weight) methyl methacrylate, 34.6 parts methanol, and 57.6 parts water was maintained at 65 C. for five days. The polymerized methyl methacrylate precipitated as formed in a finely divided state. Shaking or stirring converts the mass to a slurry. The polymer was filtered oii from the methanolwater'solution and thoroughly dried.

Example 6.-A solution of 3.3 parts (by weight) methyl methacrylate, 31.6 a parts methanol, and 65.1 parts water was maintained at 65 C. for five days. Polymerized methyl methacrylate separated as a finely divided spongy mass which on shaking or stirring could be converted to a slurry. The polymer was filtered oil from the methanolwater solution, washed with methanol, and dried.

Example 7.A solution of 11 parts (by weight) methyl methacrylate, 35 parts methanol, 54 parts water,'and 0.1 part benzoyl peroxide was maintained at 65 C. for 24 hours. A white spongelike precipitate of methyl methacrylate polymer was formed. The contents of the polymerization The polymer pre-v The polymer was filtered ofl 7 Example 9.-A solution of 20 parts (by weight) methyl methacrylateand 80 parts methanol was exposed for two days at room temperature to the light from a mercury vapor arc. Polymerization was essentially complete and the polymer was precipitated as a porous spongy mass which after filtering and drying could be readily reduced to a powder.

Example 10.--A solution of 10 parts (by weight) methyl methacrylate, 90 parts low boiling gasoline, and 0.05 part benzoyl peroxide was main- .tained at 65 C. for two days. Gasoline was illtered oil from the spongy precipitate of polymer and the product was thoroughly dried.

Example 11.A solution of 12 parts (by weight) methyl methacrylate, 88 parts cyclohexane, and 0.1 part benzoyl peroxide was maintained at 65 C. for 24 hours. By this time the methyl methacrylate appeared to be completely polymerized and the polymer was deposited as a porous spongy mass. The polymerization vessel was shaken to produce a slurry of the polymer. The polymer was filtered from cyclohexane and dried.

Example 12.-A solution of c 13.5 parts (by weight) methyl methacrylate, 86.5 parts hexane, and 0.1 part beuzoyl peroxide was maintained at 65 C, for 24 hours in a closed container. Polymerization was essentially complete by this time and the methyl methacrylate polymer was deposited as 'a porous spo y mass which could be easily stirred to a slurry. The polymer was filtered, washed with hexane, and dried.

Example 13.-A solution of 12.5 parts (by weight) methyl methacrylate, 87.5 parts heptane, and 0.1 part benzoyl peroxide was maintained at 65 C. for 24 hours. The methyl methacrylate polymerized and as polymer was formed it precipitated as a loose fiakey mass. The polymer was filtered from the heptane, washed with methanol, and dried.

Ezample'14.A solution of 10 parts (by volume) methyl methacrylate and 90 parts low boiling gasoline was exposed to the light from a mercury vapor arc in a pyrex container for 12 days. Methyl methacrylate was polymerized and the polymer was deposited as a spongy mass which could be easily broken up, washed, dried, and powdered.

Example 15.A solution of 10 parts (by volume) methyl methacrylate and 90 parts diisopropyl ether was exposed to the light of a mercury vapor are for 12 days in a pyrex container. Methyl methacrylate was polymerized and the polymer was deposited as a spongy mass. material was stirred, filtered, washed with meth'e anol, and dried first atroom temperature and finally at 120 C.

Example 16.A solution of -10 parts (by weight) methyl methacrylate, 90 parts low boiling gasoline, and 0.05 parts'benzoyl peroxide standing over 100 parts water was maintained at-65 C. for three days. Methyl methacrylate polymer precipitated as formed as a loose flakey material most of which settled to the water layer. The

- polymer was filtered from gasoline and water,

washed with methanol, and dried.

Example 17.--A mixture of 10 parts (by weight) methyl methacrylate, parts methanol,

45 parts 'hepta'ne, '100 parts water and 0.05 part benzoyl peroxide was maintained at C. for 24 hours in a closed container. Throughout this time the liquid in the reaction vessel remained in two layers. The upper layer contained the heptane and the lower layer the water. Methanol and monomer were divided between the jtwo layers, the methanol being largely in the lower layer and the monomer largely in the upper layer.-

The polymer formed as a loose fiakey precipitate largely contained in the water layer. The organic layer was removed mer was filtered from the aqueous layer. After washing with methanol, the polymer was thoroughly dried.

Example 18.-A solution of two parts (by weight) methyl'methacrylate, 81.! parts water, 16.3 parts methanol, and 0.02 part benzoyl peroxide was maintained at 65 C. for 24 hours with suflicient stirring to'keep the liquid constantly in motion. A considerable portion of the methyl methacrylate had polymerized and was suspended as loose flakes in the liquid. The polymer was filtered from the solution, washed with methanol, anddried. j

Various changes may. be made in themethod described without departing from the" invention or sacrificing any of the'advantages' thereof.

- 1. A process for the manufacturegjot resinous products by polymerization of methyl methacrylate which includes the step of subjecting methyl methacrylate to polymerizing conditions while dissolved in a watermiscible aliphaticalcoholwater solvent medium in which the polymerization product is sufliciently insoluble to precipitate the polymerization product as a light fiufiy 2. A-process for the manufacture or products by polymerization of me i methacrylby decantatlon' and the polymethyl methacrylate as a light ing the polymer from the solution,

' polymeric methyl methacrylate as a ate which includes the step of subjecting methyl methacrylate to polymerizing conditions while dissolved in a water miscible aliphatic alcoholwater solvent medium'in which the polymerization product is suihciently insoluble to precipitate the polymerization product as a light fiufiy powder, thereafter separating the polymerization product from the solvent medium, washing the former with a solvent for the monomeric material and drying the washed material.

3. Process of claim 1 wherein the monomer and solvent medium are subjected to agitation during polymerization.

4. Process of claim 1 in which the solvent medium comprises a mixture of water and methanol.

5. Process of claim 1 in which the proportion of monomer to monomer plus solvent medium is not more than 22% by volume.

6. A process for the manufacture of polymeric flufly powder which includes the steps of subjecting monomeric methyl methacrylate to polymerizing conditions while dissolved in a water-methanol solvent (the amount of monomer being not more than 22% by volume of the total liq 'd), thereby precipitating polymeric methyl methacrylate in pulverulent form, thereafter separating the polymer from the bulk of the liquid and removing from the polymer the monomer adhering thereto.

'7. A process for the manufacture of polymeric methyl methacrylate which includes the steps of subjecting a solution containing approximately 2 partsby weight of methyl methacrylate, approximately 81.! parts of 'water, approximately 16.3 parts of methanol and approximately 0.02 part of benzoyl pero tie to a temperature in the neighborhood of 65 C., and continuously stirring for approximately 24 hours, subsequently filterwashing with methanol, and drying and thereby obtaining the l t flu!!! powder.

DANIEL E. STRAIN. 

